Means for producing hollow billets for hollow drills and the like



C, J. GEJROT Jan. 12, 1937.

4MEANS FOR PRODUCING HOLLOW BILLETS FOR HOLLOW DRILLS AND THE LIKE Filed July 23. 1934 I nlil|I||IHHHHHHH I nnnuuundn..

Patented Jan. 12, 19.37

PATENT' OFFICE LIENS FOR PBODUCING HOLLOW BILLETS FOR. HOLLOW DRILLS AND THE LIKE Claes Joel Gejrot, Bofors, Sweden, assignor to Aktiebolaget Bofors, Botors, Sweden, a limited company Loi' Sweden ApplicationA July 23, 1934, Serial No. 736,584 In Sweden July 29, 1933 Claims.

'Ihe present invention relates to the manufacture and production of hollow bars or other tubular or hollow bodies, such as hollow ingots for hollow drills and the like, vand may be regarded as an improvement of the invention disclosed in my copending application, Serial No. 697,987, filed November 14, 1933.

As described in my above ldentied application such hollow bodies are produced by casting molten metal from below around an insert or tube inserted into a mould, which is provided with a discard head box arranged in the upper part of the mould. In said method the casting is carried out, either in small moulds having only one mould chamber or, preferably, in moulds containing a plurality of mould chambers, below connected with a common inlet channel for the molten metal, each of said mould chambers being provided 'with a discard head box arranged in the upper part of the mould chamber around the tube inserted therein.

According to the preferred embodiment of the invention disclosed in my above-mentioned application, said discard head box is given such a shape that it, with the exception of a hole for the tube as well as necessary vent openings arranged therein, closes the mould or mould chamber at the top. The top end of the tube extending through said hole at the top of the discard head box is secured in place by means of a cover placed on the mould, said cover having a hole which receives the upper end of said tube, and Vent openings between the walls of said holey and said tube. In other respects the features of the method and means set forth in my prior application may not be described for the purpose of avoiding repeating.

In the embodiment of my prior invention described above, the core, as will be seen from the foregoing, extends through the whole discard head. Consequently, that part of the core which is located withinthe discard head will be removed With the latter and be lost. This, however, is a great disadvantage, especially if the core material is expensive, as'is often the case, for instance in the production of hollow billets for hollow drill steel, where use is made of a tubular core of stainless steel.

The object of the present invention is to obviate said disadvantageand save expensive material by providing means whereby it becomes possible to carry out such a casting operation in a mould provided with a discard head box, without having the corev or insert tube enter or project into or through the whole of the discard head, yet ensuring that the desired position of the core or insert tube is maintained, in the centre of the mould or otherwise. l

For that purpose, according to this invention, the core or insert tube is arranged in such a way that it ends below the top of the discard head box arranged in the upper part of the mould or mould chamber, and the top end of the tube is secured in place by means of a centering mem-y ber arranged in the upper part`of said mould or mould chamber. For convenience, the term "centering is used to designate the securing in place of the tube, whether this be in the centre of the mould chamber or otherwise.

According to a preferred mode of carrying out this invention, the` tube is arranged in such a way that it extends slightly into the .lower part of the discard head box,y where the centering of the top end of the core is effected by means of a centering member inserted into or embracing the .tube or arranged on top of the tube.

In the accompanying drawing the new means for carrying out the method of manufacture of hollow bodies according to the invention are illustrated by way of example.

Fig. 1 is an elevation, partlyin vertical section, 'of' a mould containing a plurality of mould chambers, only one of which is shown in section, said mould chamber being in the upper part provided with a discard head box.l and a centering memberfor the tube inserted therein.

Fig. 2 is a section on a larger scale through. the upper part of Fig. 1 taken on the line II--H in Fig. 1.

Fig. 3 shows a section through the upper part of a mould where the discard head box itself serves as the centering member.

Fig. 4 shows another embodiment of the centering member'and Fig. 5 is a section on the une v v of Fig. 4.

Referring to Figs. -1 and 2, I designates the mould, in which a plurality of mould chambers IIl, in this case ve, are arranged. The bottom of the mould consists of receptacles, or runner bricks, II of refractory material arranged closely together, one plate for each mould chamber, said runner bricks being provided with a central channel I2 forming an intake channel for the molten cast metal and common to the whole mould. One end of the channel I2 communicates with a box I3 provided with acomman inlet opening I4 for the molten metal, whereas the opposite end of the channel is plugged. From the channel I2 two inlet openings I5 lead to each of the mould chambers above the runner bricks II. On the top sides of the runner bricks I I there are provided recesses I6 for centering the lower end of the tubes inserted into thev mould chambers.

At the upper end each mould chamber is provided With'an enlargement 2 in the inside wall of the mould chamber, the bottom of said enlargement being deiined by a shoulder 3 in the mould wall. In said upper part of the mould chamber there is inserted a thin plate 4 serving as a discard head box. As'shown in Fig. 2, said plate 4 at the lower end is provided with outwardly bent (or welded thereto) strips 5 bearing against the .shoulder 3, the lower edge of .the plate projecting into the mould below'the shoulder 3, as indicated by numeral 6 in Figure at the edges of the hole in said plate l.

2. Towards the top, the plate 4 is contracted to form a box, which at the top is provided with an opening or a hole for the upper end of the centering member 8 arranged on top of the tubular core 1 inserted into the mould chamber and extending slightly into the lower part of the discard head box. The mould also is provided with a cover 9 with handles I9, said cover having a hole II, which receives the upper .end of said centering member 8 and secures it in place. Said cover also is provided with vent openings I8, corresponding vent openings being arrancgd e top part of the plate preferably is so dimensioned, that, whenv the cover 9 is not put in place, the plate projects somewhat above the vtop surface of the mould and so that when lsaid cover is put in place on the mould, the plate will be pressed down to bear against the sides of the centering'member 8.

Before 'putting the cover in place, the space around the discard head box is iilled with sand,

asbestos or some other suitable insulating mateing member '8 consists of a tube constituting an Vanother core 22 inserted in it, as also shown in the iigures, be loosely put on top of the expensive tube, the inserted core extending through both parts ofthe tube. If it is desired to use an inserted core, which does not extend to the bottom of the mould, the top end of said core may be provided with a flange or collar. (not shown) adapted to bear against the top end of said tube extension 8.

In case of using a tubular insert with a core inserted therein, the tube extension 8 also may be dispensed with, provided that the projecting part of said inserted core 22, ,as shown in the gures, projects sufficiently from the upper end of the tubular insert to permit the centering of said tubular insert. -In such a case, the projecting part of the inserted core serving as a centering member suitably may be covered with graphite, clay or other suitable material in order to prevent the molten metal from. welding to the same. Further, said projecting part may be provided with anges or collars (not shown) for keeping said inserted core, axially or radially, in the right position. In all the above-mentioned casesr where use is made of a tubular insert with a. core inserted therein, the latter, instead of being tubular, also may be solid.

Referring to Figures 3 to 5, said gures show moulds having only one mould chamber. It is, however, evident that the arrangement shown in said figures also may be used in moulds having Ya plurality of mould chambers.

According to the modification shown in Fig. 3 the centering member for the core constitutes a p'art of the discard head box 4a itself. Thus, the central part of said discard head box is given Va downwards projecting form 8a, which enters the top end' of the insert tube 'I and serves as a centering memberfor the same. By giving this centering member a tapered Vform it will be possible to vary the diameter of the insert without altering the discard head box, by merely varying the length of the insert. The plate 4a, which at the top is provided with the vent opening 20, may be made of sheet iron or sheet steel, preferably corrugated or provided with undulations in order to make it stiier and more resistant. Also, for the same purpose, the space 2I between the walls of the part 8a of the discard head box may be filled and packed with sand, asbestos or fire proof materials, which at the same time serve as heat-insulating materials. Obviously, instead of the discard head box being made of sheet iron or sheet steel, it may be made of refractory material, in which case the use of special insulating material may be dispensed with.

In Figures 4 and 5 the centering member consists of a cross-piece 8b in the centre provided discard head box 4b. In/ this case, the top end ofthe insert, if tubular, must be plugged or otherwise closed for preventing molten metal to iiow` into the tube.

In Figures 3 and 4 the lower ends of the discard head boxes are shown-as bearing against the shoulders 3, but the vsame may also be shapedwith projecting parts and strips as indicated by numerals 6 and 5 in Fig. 2. Further, the moulds also may be provided with covers.

It is understood that the invention is not limited to the precise details of construction and arrangement herein set forth, as it is obvious that various modiiications may be made'therein withoutl departing from the spirit of the invening, in combination, a mould having inlet openings at its bottom. a heat insulated discard head box made of sheet metal arranged in the upper part of the mould chamber, a tube inserted into said mould with its upper end extending slightly into the lower part of said discard head box,

means for positioning the lower end of said tube at the bottom of said mould chamber, a centering member for the top end of said tube arranged on top of the tube and constituting an extension of cheaper material of the tube proper, said discard head box being tapered upwards towards its top and arranged to bear, at its bottom against the Walls of said mould chamber and with its upper end against said tube extensions which box, with the exception of vent openings arranged therein, closes the mould at the top.

2. Means as claimed in claim 1, characterized therein that said tube extension is united with Y the top end of the tube proper.

3. Means as claimed in claim 1, characterized therein that said tube extension is loosely put on top of the tube proper by means of a core inserted into and extending through lboth parts of the tube.

4. Means as claimed in claim 1. characterized therein that the top end of said tube extension is secured in place at the top of the discard head box by means of a cover placed on the mould and provided with a hole which receives the top end of said tube extension.

5. Means for casting hollow bodies comprising, in combination, a mould having'inlet openings at its bottom, a discard head box arranged in the upper part of the mould chamber, which box, with the exception of necessary vent openings arranged therein, closes the mould chamber at the top, a tube inserted into said mould with its upper end extending slightly into the lower part o! said discard head box, means for positioning the lower end of said tube at the bottom of said mould chamber and a. centering member for the top end of said tube consisting of a crosspiece arranged in the lower part of said discard head box, in the center provided with a hole, which receives said tube and with its arms bearing against the walls of the mould chamber.

CLAES JOEL GEJROT. 

